Shoe stiffener



Patented July 9, 1940 UNITED STATES PATENT OFFICE SHOE STIFFENER N0 Drawing. Application February 19, 1940, Serial No. 319,686

8 Claims.

This invention relates to shoe stiffeners, such as box toes, counters and the like. It consists in an improved stiffener, oran improved sheet material for stiffeners, having certain advantages in structure and in economy of manufacture which will be hereinafter pointed out.

Shoe stiffeners have been made heretofore by saturating bibulous fabrics with stiffening compounds capable of being temporarily softened by heat or solvent, or from special woven or felted fabrics containing with the usual fibres a mixture of fibres of soluble material, such as cellulose acetate or Vinyon, as an inherent part of their structure. In the latter case these soluble fibres may be partially dissolved or softened to form a liquid which when dried and hardened acts to stiffen the fabric. However, the degree of stiffening thus obtained is not adequate for many present shoemaking requirements.

The object of the present invention is to combine in one article of manufacture the advantages of a woven or felted textile structure having stiffening fibres actually incorporated in its structure, and also of a fabric carrying a stiffening saturant or coating distributed therein. I have discovered that in making this novel combination I achieve results of unexpected value and importance in the shoemaking industry. For example I am thereby able to produce economically a shoe stiffener having greatly increased resilience and stiffness without any objectionable increase in bulk or thickness. Further, I am able to produce a shoe stiffener having not only the properties normally found in stiffeners of the thermoplastic type heretofore known, but with greatly increased resilience.

These and other features of the invention will le best understood and appreciated from the follc vlng description of several preferred embodiments thereof selected for purposes of illustration.

As a fabric base I prefer for purposes of my invention to employ a woven or felted sheet comprising carrier fibres selected from the group, wool, jute, cotton, and flax, although any other suitable fibre not soluble in organic solvent may be employed according to the specific requirements of the work in hand. By the term carrier fibres I mean the fibres of the fabric which re.- main unchanged or substantially unchanged throughout various treatments to which the stiffener is subjected in the shoemaking process and which may be relied upon to supply tensile strength to the fabric both in its pliable condition and-when stiffened in the lasted shoe. With the carrier fibres are mixed or woven stiffening fibres of material which is adapted to be dissolved, or partially dissolved by a solvent or softened when subjected to heat. Cellulose acetate is one suitable material for the stiffening fibres or I mayemploy for this purpose any material which may be dissolved or liquefied by an organic solvent with out chemical reaction, and which reassumes its solid form upon being dried. Other suitable materials for the stiffening fibres are vinyl esters, and ethyl cellulose. Fibers made of these ma- 1O terials are heat responsive and may be softened either by the application of heat or by solvent. As a thermoplastic saturant I may use rosin, montan wax, candelilla wax or compounds thereof I have found that in some instances it is ad- 15 visable to add a rubber or rubber-like ingredient to the thermoplastic compound for the purpose of reducing brittleness and dustiness in the product.

A fabric base of woven or felted construction comprising 85% to 70% cotton fibre and 15% to 30% cellulose acetate fibre has proved very satisfactory for purposes of my invention. While such a fabric is stiffened to some extent by the mere treatment with solvent such as acetone and subsequent drying so that the dissolved material forms a hard film, if an excessive amount of the soluble stiffening fibre is employed in the composition of the fabric it is obvious that the fabric base may lose strength or even disintegrate when treated with the solvent. This would prove objectionable from the shoemaking standpoint because it is essential that the softened stiffener should retain sufficient strength and toughness when soft to withstand the lasting strains without tearing or thinning down in the shoe. The material of my invention always contains a sufficient proportion of insoluble fibres to avoid this weakness.

In accordance with the present invention I add to the potential stiffening effect of the soluble fibres the effect of a definite and controlled amount of stiffening compound. For example, I may add a thermoplastic saturant to such a base;a saturant, comprising rosin, montan wax or other thermoplastic ingredients or compounds. The thermoplastic compound is preferably uniformly distributed throughout the structure of the fabric base as a saturant, coating or impregnating both the carrier fibres and the stiffening fibres thereof. Thus is provided a sheet material comprising a fabric base made up of carrying fibres selected from the group, wool, jute, flax and cotton, in combination with soluble or heat-reactive stiffening fibres, soluble in an organic solvent while the base as a whole car- 55 ries a substantially uniformly distributed thermoplastic saturant upon all of its fibres. Box toe blanks may be cut from this sheet material and when used will be found to have great stiffness and resilience in the finished shoe but without objectionable tendency toward brittleness and dustiness, and offering great resistance to distorsion even at the excessively high temperatures sometimes encountered by shoes in show windows or in storage and transportation.

As another desirable embodiment of my invention I may add to the composite base above described a saturant in the form of a solvent softenable stiffening compound, such as pyroxylin or other esters or ethers of cellulose. Thus I produce sheet material comprising a fabric base made up of carrying fibres selected as before from the group, wool, jute, flax, and cotton, in combination with stiffening cellulose fibres soluble in an organic solvent and a uniformly distributed pyroxylin saturant upon all the fibres of the base. The individual shoe stiffeners may be cut from this base sheet and when treated with solvent in the shoe factory, the softening action on the original soluble fibres bonding the fabric is noticeable and the additional stiffening-compound is also rendered plastic by the solvent so that the blank becomes pliable and plastic for the lasting operation, although it still maintains sufficient strength and toughness by reason of its carrier fibres to withstand the strains to which it is subjected. When evaporation of the solvent takes place, the blank acquires a degree of hardness and resilience not heretofore approached by stifieners of the same thickness. This is true because not only is the load or saturant or stiffener colloid transformed into a hard film, but a very appreciable part of the fabric base itself consisting of the soluble fibres is now transformed to a hardening agency. Accordingly it is possible to produce the same degree of hardness in a much thinner box toe than heretofore, a very desirable characteristic from the shoemaking standpoint, or by maintaining present standard of thickness it is possible to produce a box toe of greater stiffness than has been available heretofore.

This will be apparent when it is considered that if it is not practical to load into a cotton fabric base more than 100% by weight of dry stiffening compound, now by integrating into a composite base 30% of stiffening fibres, for example, it is possible to bring the combining stiffening ingredients of the blank up to 130% of the weight of the base.

In general it may be said that all fibres desirable for the stiffening function that are soluble in organic solvents without essential chemical change in their molecular structure are also responsive to heat, that is, they may be softened by moderate heating. This is true of most of the cellulose ethers and esters, the polyvinyl acetates and chlor-acetates and the like. It will be apparent that a shoe stiffener base comprising fibres neither thermoplastic or soluble and other fibres both soluble and thermoplastic may be impregnated with a thermoplastic compound, if a thermoplastic stiffener is desired, or with a soluble stiffening compound if a solvent softenable toe stiffener is required.

Having thus disclosed my invention and described certain preferred embodiments thereof for purposes of illustration but not in any limiting sense, I claim as new and desire to secure by Letters Patent:

1. As a new article of manufacture, a shoe stiffener comprising a. fibrous base having some fibres thermoplastic and soluble in an organic solvent and other fibres insoluble in an organic solvent and all of said fibres, both soluble and insoluble, carrying an additional stiffener compound responsive to a softening agency.

2. A shoe stiffener sheet comprising a base which consists of a mixture of fibres soluble and insoluble in an organic solvent and carries a substantially uniform load of stiffening material soluble in an organic solvent upon all of its fibers.

3. A shoe stiffener comprising a base consisting of approximately to 30% of fibres which are soluble in an organic solvent and 85% to 70% fibres which are insoluble in the same, and a substantially uniformly distributed load of stiffening compound soluble in an organic solvent.

4. As a new article of manufacture, a shoe stiffener comprising a fibrous base consisting of fibres thermoplastic and soluble in an organic compound and other fibres insoluble in the same and not thermoplastic, the base carrying a substantially uniformly distributed load of a thermoplastic compound.

5. A shoe stiffener comprising a fabric base of sheet material made up of carrying fibres selected from the group, wool, jute and cotton, in combination with stiffening cellulose fibres soluble in an organic solvent, the base carrying a substantially uniformly distributed pyroxylin saturant upon all of its fibres.

6. A shoe stiffener comprising a fabric base of sheet material made up of carrying fibres selected from the group, wool, jute and cotton, in combination with stiffening thermoplastic and soluble in an organic solvent, the base carrying a substantially uniformly distributed thermoplastic saturant upon .all of its fibres.

7. A shoe stiffener comprising a fabric base of sheet material made up of carrying fibres selected from the group, wool, jute and cotton, in combination with stiffening cellulose fibres thermoplastic and soluble in an organic solvent, the base carrying a substantially uniformly distributed thermoplastic and rubber saturant upon all of its fibres.

8. A shoe stiffener comprising a fibrous base of which about 15% to is made up of pyroxylin fibres and 85% to 70% is made up of fibres selected from the group, wool, jute, and cotton, the base carrying about an equal weight of dry pyroxylin saturant and thus presenting a stiffener blank in which solvent-softenable stiffening material comprises about 130% of the weight of the base.

STANLEY P. LOVELL.

cellulose fibres" 

